A typical disk drive includes a housing having a base, a top cover and a printed circuit board assembly (PCBA). The housing encloses at least one disk that is rotated by a spindle motor and an actuator assembly is used to position one or more transducers along each disk to read and/or write information to particular locations on each disk. The transducers are mounted to a suspension of the actuator assembly. The suspension maintains the transducers adjacent to or in contact with the data surface of each disk. A voice coil motor is used to precisely position the actuator assembly. Typically, the PCBA is mounted under the base plate to isolate it from components, which are enclosed by the housing.
The top cover can include a laminated design having multiple layers. The layers of the top cover are bonded together by a visco-elastic adhesive. The adhesive layer provides acoustic isolation to prevent undesirable acoustics from propagating beyond the housing of the disk drive, which otherwise might deleteriously effect operation of the computing device in which the disk drive is installed.
During operation of the disk drive, heat is generated from the disk drive components, creating thermal stresses on the disk drive housing. Because of the dimensional variation of the individual layers in the top cover, as well as the different materials that may comprise the top cover, thermal stresses can cause delaminating of the layers. Additional forces can also be transferred to the top cover, such as bending stresses caused by the particular geometry of the top cover and the position of the securing screws that secure the top cover to the base of the housing. For example, when the securing screws are tightened, stresses are transferred to the top cover that can also contribute to delaminating of the layers of the top cover. The combined thermal and screw induced stresses can ultimately cause adhesive failure of the adhesive layer, and significant separation of layers of the top cover. Separation of the layers can result in inadequate acoustic control, as well as violation of form factor requirements of the disk drive.